Limit Cycle Oscillations of Aircraft due to Flutter-Induced Drag

The present work is a continuation of earlier work by the author on the energetics of flutter. It has been shown in earlier work that the energy for flutter comes from propulsion, i.e., flutter leads to increase in drag and thus the thrust has to be increased in order for the wing to maintain instability. In reality, the thrust is not increased to maintain the speed while the wing goes into flutter. The present paper seeks to explain the effect of flutter-induced drag on the response of the aircraft. It is shown that the aircraft can undergo limit cycle oscillations (LCOs) even if the oscillations are in the linear structural and aerodynamics lift ranges. This LCO occurs due to the inability of the engine to support exponentially increasing oscillations. Such a LCO is composed of variations in airspeed and amplitude of vibration. This modality of LCOs has not been presented in the literature before and leads to better understanding of the LCO problem.